WO 2007/044472 discloses an LED assembly with a light transmissive heat sink. The LED assembly is formed from a high power LED chip having a first surface and a second surface, the first surface being mounted to a substrate, and the second surface being in intimate thermal contact with a light transmissive heat sink having a thermal conductivity greater than 30 watts per meter-Kelvin. Providing the light transmissive heat sink can double the heat conduction from the LED dies, thereby increasing life, or efficiency, or luminance, or a balance of the three. It is further mentioned that a laser diode may be used as a light producing device instead of an LED.
US20160131336A1, among other, shows a laser-based light source using a semispherical lens with good heat conducting capabilities functioning as substrate to grow a wavelength converter onto it. By such construction, the heat generated on wavelength conversion in the wavelength converter can be advantageously radiated away by the lens.
The overall efficiency of the LED or laser assembly may be low.